"In an Instant" Airing on "20/20? Friday, April 19 at 10 pm on ABC

In the moment of crisis, lives can change drastically by twists of fate and split-second decisions. "20/20? reports on surviving, from random violence and acts of terror, to massive highway accidents, to the madness of crowds and stampedes. "20/20?airs on FRIDAY, APRIL 19 (10:00-11:00 p.m., ET) on ABC.

John Quinones reports on the split-second decisions that could make the difference between life and death during a potentially deadly highway pile-up.

What makes a difference between life and death when there is an active shooter in the office? Elizabeth Vargas speaks with workplace shooting survivors and a law enforcement official who demonstrates what to do.

"20/20? explores the phenomena of "crowd think" and the herd mentality of stampedes, where individuals forget logical thinking and instead follow everyone else even if it is clearly not the right thing to do.

Amputee college soccer player Bree McMahon shares her inspiring story of recovery, and "20/20? is with her as she visits Boston to support the amputee victims whose lives changed in an instant on Monday. Deborah Roberts reports.

"20/20? is anchored by Elizabeth Vargas and David Muir. David Sloan is executive producer.